Investigation of recurrent deletion loci specific to conventional renal cell carcinoma by comparative allelotyping in major epithelial carcinomas

Abstract

Objective: Loss of heterozygosity (LOH) studies were undertaken to investigate the consistently deleted loci/? tumor suppressor gene loci (TSG) on 3p in conventional renal cell carcinoma (cRCC).

Materials and methods: LOH studies were performed by polymerase chain reaction (PCR) using 15 micro satellite markers mapped in region 3p12-p26 on 40 paired cRCC tumors and normal kidney at Stages I-IV. Simultaneously, fluorescent in-situ hybridization (FISH) studies were performed to investigate the allelic deletion of fragile histidine triad (FHIT).

Results: Our studies revealed three affected regions; 3p12.2-p14.1, 3p14.2-p21.1, and 3p24.2-p26.1 with differential frequencies in Group I (Stage I and II) and Group II (Stage III and IV). Incidence for D3S1234 (FHIT locus) and D3S2454 (3p13) was 75% and 83% in Group I and II, respectively. Comparative allelotyping in epithelial malignancies like lung, bladder, and breast tumors revealed LOH (frequency 14-20%) only in breast tumors for D3S2406, D3S1766 (distal to FHIT), and D3S1560 (distal to VHL, Von-Hippal Lindau). FISH using FHIT gene probe revealed deletions in cRCC (88%), breast (30%), and lung tumors (10%) with no deletions in bladder tumors and leukemias, signifying the importance of FHIT in the pathogenesis of tumors of epithelial origin.

Conclusion: Our findings suggested FHIT deletion as an early and VHL deletion as an early and/or late event in cRCC. Additionally, studies also disclosed the recurrent deletions of flanking loci to FHIT and VHL in cRCC. The dilemma of interstitial or continuous deletion on 3p needs to be resolved by implementation of latest sensitive molecular techniques that would further help to narrow down search for TSG loci specific to cRCC, other than VHL and FHIT.

Keywords: 3p; Conventional renal cell carcinoma; comparative allelotyping; fragile histidine triad; interstitial deletion; von hippal lindau.

Figure 1

Chromosome 3p ideogram showing loss of heterozygosity (LOH), retention of heterozygosity (ROH), and micro satellite instability (MSI) for micro satellite markers mapped on 3p according to location database (LDB) in cRCC.

Figure 2

(a) LOH at locus 3p12.2 for micro satellite marker D3S2406 in cRCC. (b) MSI in both alleles at locus 3p21.1 for marker D3S1766 in cRCC. (c) Heterozygous MSI at locus 3p14.1-p14.2 for marker D3S1285 in cRCC. (d) Homozygous allelic pattern at locus 3p21.3 for micro satellite marker D3S2409 in cRCC. (e) LOH at locus 3p21.1 for marker D3S1766 in breast carcinoma. N: Normal DNA T: Tumor DNAL

Figure 3

Chromosome 3p ideogram showing loci of LOH and MSI in defined regions R1, R2, R3, and R4 in cRCC patients. It also indicates differential LOH frequencies in Group I (Stage I and II) and Group II (Stage III and IV).

Figure 4

Chromosome 3p ideogram showing common LOH loci in defined regions R1, R2, R3, and R4 in cRCC and breast